Project Summary: Neurodegenerative diseases are a rising public health concern with limited treatment options. Neurodegenerative diseases are associated with cell stress including the accumulation of misfolded proteins in the endoplasmic reticulum (ER). When the protein folding capacity of the ER is overwhelmed, ER stress occurs, resulting in the initiation of the unfolded protein response (UPR) to regain homeostasis. However, unresolved UPR activation leads to cell death and aberrant inflammation. Astrocytes are the most populous cell in the central nervous system (CNS) and are largely resistant to ER stress-induced cell death. Recent evidence indicates ER stress and inflammation are linked. We have found that UPR activation in astrocytes activates JAK1-dependent inflammatory gene expression. Canonical JAK1 signaling is initiated by ligand binding of a cytokine receptor that results in Signal Transducers and Activators of Transcription (STAT)-dependent inflammatory gene expression. Previously, using RNA sequencing of primary murine astrocytes, we have demonstrated that JAK1 regulates approximately 10% of ER stress-induced gene expression. However, we found JAK1 initiates different gene expression based on the activating stimulus. Our central hypothesis is that cell stress induces JAK1-dependent inflammation in astrocytes that contributes to a neurotoxic environment in the CNS. In response to ER stress, JAK1 regulates a distinct subset of gene expression that we hypothesize does not rely on JAK1-dependent tyrosine kinase activity. First, we will generate and characterize astrocyte-specific JAK1 knockout mice. We anticipate that these astrocytes will have reduced capacity to respond to cytokines and ER stress. Further, we will use the mouse model Experimental Autoimmune Encephalomyelitis (EAE), a model of Multiple Sclerosis and generalized neuroinflammation, to study the cell-specific contributions of JAK1 signaling in a pathological state. To expand on the nature of noncanonical JAK1 signaling, we will use in vitro molecular biology and bioinformatics techniques to gain mechanistic insight on the cell stress-induced molecular mechanisms of JAK1 signaling in astrocytes. We anticipate that JAK1 signaling in astrocytes drives inflammatory gene expression in the CNS. However, ER stress will drive distinct gene expression without utilizing the kinase activity of JAK1. The long-term goal is to elucidate therapeutic targets for neurodegenerative conditions that attenuate damaging inflammation while leaving the beneficial immune response intact and avoiding broad immunosuppression.